Obesity rates have been rising
A diabetes injection appears more effective at promoting weight loss than one of the leading obesity drugs, trials suggest.
Patients receiving liraglutide, which contains a satiety hormone, were twice as likely to lose significant amounts of weight as those on orlistat.
Not only does the drug appear to curb hunger, it also reduces type 2 diabetes risk factors, the Lancet study found.
The study author is a paid consultant of the company which produces the drug.
There are limitations: the drug must be injected every day as it would otherwise be broken down in the gut, and it is expensive - £500 for six months of treatment.
Further studies are needed to establish the longer term risk-benefit ratio as this trial on 564 patients ran for just 20 weeks.
Over this period, three groups of patients in 19 hospitals were put on a diet reduced by 500 calories a day and asked to exercise.
One set received a placebo, the second orlistat - available by prescription as Xenical - and a third liraglutide, also known as Victoza.
Over the 20 weeks, more than three quarters of those on 3mg of liraglutide lost more than 5% weight, compared with 44% with 120mg of orlistat and 30% with a placebo.
This on average translated as more than a stone in weight.
Professor Arne Astrup, head of the department of Human Nutrition at the University of Copenhagen, Denmark, who led the study, said: "The reason why we think this drug is so intriguing is that it mimics a gut hormone called GLP-1 which is released in the small intestine after eating.
"It tells the body to produce more insulin and the brain to stop eating. It is a naturally occurring satiety hormone. The problem is that it is eliminated from the blood stream within minutes. The company [Novo Nordisk] has added a molecule to make it more resistant to elimination, so it lasts for a full day."
Professor Astrup has received funding from Novo Nordisk, but is regarded as an authoritative voice on obesity.
In an accompanying editorial in the Lancet, Dr George Bray of the division of clinical obesity at Louisiana State University, said he was optimistic the promise of the new generation of anti-obesity drugs "will be fulfilled".
But he warned: "Whether long-term use of an injectable drug is palatable as a treatment for obesity is yet to be established."
The search is on for the most effective ways to treat obesity and its accompanying health risks: in the UK alone it is estimated that more than half of men and women will end up obese if current trends continue.
This study involved volunteers aged 18-65 from across Europe, with a body mass index of between 30 and 40 - a calculation reached by by dividing weight in kilograms by height in metres squared.
Dr Ian Campbell, of the charity Weight Concern, said: "It's important that we continue to develop good weight loss drugs.
"They can help some people lose weight more quickly than diet and exercise alone.
"The problem is that once treatment has stopped, unless diet and exercise are continued, weight lost is quickly regained.
"The greater emphasis therefore has to be on finding ways to support people in changing their lifestyle, to become more active, and to eat healthily."
More research needed
Caroline Butler, Care Advisor at leading health charity Diabetes UK, said: "It is already established that liraglutide widens the choice of treatments for people with Type 2 diabetes as it offers not only improved blood glucose control but may also aid weight loss.
"However, liraglutide's role in aiding weight loss in obese people without diabetes is questionable and more research would need to be carried out before any conclusions are reached."
Roche, which makes Xenical, said: "Taken as an oral treatment, orlistat has been shown to significantly reduce weight when used in conjunction with healthy low fat diet and is the most widely studied drug for obesity.
"Its mechanism of action by impeding the absorption of fat can lead to long-term behavioural change and consequential weight loss has a positive impact on risk factors for cardiovascular disease."